OBJECTIVE To clone cDNA of chicken LHRH-II in the monkey midbrain. Previously, we have shown the presence of a second form of LHRH, chicken LHRH-II (cLHRH-II), in the monkey brain (Endocrinology, 138 5618, 1997) 1) cLHRH-II immunopositive cells were found in the midbrain of adult and fetal rhesus monkeys with specific antisera, and 2) a peak corresponding to cLHRH-II, distinct from mammalian LHRH, was identified by HPLC from extracts of adult stumptail monkey brains as well as adult and fetal rhesus monkey brains. In order to further identify this second form of LHRH in the non-human primate brain, we carried out RT-PCR on adult rhesus monkey brainstem mRNA with primers based on a portion of the upstream signal peptide and the downstream processing region of tree shrew cLHRH-II cDNA. The resulting PCR product was cloned and sequenced. The cDNA sequence encoding the cLHRH-II decapeptide in the monkey midbrain was identical to that reported in humans and only differed by one nucleotide substitution from that reported in the tree shrew. Further, the cD NA region for the signal peptide in the primate midbrain showed 80.5% sequence identity to that in tree shrews, and 90.3% sequence identity to that in humans. The corresponding amino acids, deduced from the signal peptide of the cDNA of the rhesus monkey, showed 75% sequence identity to that in tree shrews, and 87.5% sequence identity to that in humans. Therefore, cLHRH-II is present in the midbrain in the rhesus monkey, and this form of LHRH is well conserved throughout vertebrate evolution. FUTURE DIRECTIONS We will examine the distribution pattern of cLHRH-II mRNA in the brain. KEY WORDS chicken LHRH-II, cDNA, LHRH isoforms, mammalian LHRH, midbrain. FUNDING NIH HD15433 & RR00167 PUBLICATIONS Abler, L., Sherwood, N. M., Grendell, R. L., Golos, T. G., and Terasawa, E. 1998. cDNA of a second form of luteinizing hormone-releasing hormone, chicken LHRH-II, isolated from the non-human primate brain. Abstracts of the 28th Annual Meeting of the Society for Neuroscience 28 1607 (No. 632.8).